Numerous processes for the allylation of alkyl phenols are known. U.S. Pat. No. 2,968,679 discloses a process wherein phenol is converted to sodium phenoxide followed by the reaction of a substantially anhydrous suspension of sodium phenoxide and finely divided sodium hydroxide with allyl chloride in a nonpolar solvent. This process suffers from poor yields and is not selective for alkylation at a specific site on the phenolic nucleus.
S. Yamada et al., Bull. Chem. Soc. of Japan, Vol. 50, (3) 750 (1977), discloses a reaction wherein phenols (phenol, hydroquinone, resorcinol, and o-cresol) are reacted with prenyl halides (3-methyl-2-butenyl chloride and geranyl chloride) in the presence of an alkali metal (Na) in ether. In these reactions, phenols with the corresponding prenyl group at the ortho position were obtained selectively.
U.S. Pat. No. 3,198,842 discloses a continuous process for the ortho-allylation of phenol by percolating a solution of .beta.,.gamma.-alkenyl halide in an anhydrous inert nonpolar hydrocarbon solvent through a solid alkali metal salt of a phenol at a temperature from 0.degree. C. to 100.degree. C.
U.S. Pat. No. 3,526,668 discloses a method for producing an allyl phenol which consists of contacting an alkali metal salt of a 2,6-disubstituted phenol with a primary allyl halide in an organic solvent at a temperature from 25.degree. to 300.degree. C. to form a 2,6-disubstituted p-allyl phenol.
The prior art does not disclose or suggest that a triphase catalyst can be used to produce 2,6-di-t-alkyl-4-alkenyl phenols. Those skilled in the art are constantly searching for new processes to produce 2,6-di-t-alkyl-4-alkenyl phenols since these compounds are valuable as chemical intermediates and antioxidants. The process of the present invention provides for the use of triphase catalysts that have the advantages over what is presently known in the art in that high yields are obtainable of a specific product, elimination of high cost solvents and reaction equipment, reuseable catalysts and easy work-up of the product.
Triphase catalysis is an unique form of heterogeneous catalysis in which the catalyst and each of a pair of reactants are located in separate phases. A discussion of triphase catalysis systems, their preparation and mechanisms can be found in Regen, S. L.; Angewandte Chemie, Int. Ed. Vol. 18, No. 6, (6-1979) pages 421-492, said publication is herein incorporated by reference.
The process of the present invention is limited to triphase catalysts wherein the catalytic resin is either a macroreticular or microreticular polystyrene resin modified so as to contain quaternary phosphonium or ammonium salts.
A review of functionalization of crosslinked polystyrene resins by chemical modification can be found in Chemistry and Properties of Crosslinked Polymers, Academic Press, Inc. Santokh S. Labana, Editor (1977), pages 59 et seq., said publication is herein incorporated by reference.
M. S. Chiles and P. C. Reeves in Tetrahedron Letters No. 36, pp. 3367-3370, Pergamon Press Ltd. (1979), disclose phase transfer catalysts anchored to polystyrene. More specifically, they teach that quaternary phosphonium and ammonium salts attached to polystyrene resins by short (2-3 atom) carbon chains are highly active phase transfer catalysts for a variety of nucleophilic substitution reactions. The synthetic utility of these catalysts was explored by examining the reactions of a variety of nucleophiles with 1-bromopentane under phase transfer conditions. Chiles and Reeves disclose nucleophilic substitution reactions described generally by the equation ##STR1## wherein Nuc.sup..crclbar. is selected from the group consisting of CN.sup..crclbar., 1.sup..crclbar., Ph--O.sup..crclbar., Ph--S.sup..crclbar., N.sub.3.sup..crclbar., SCN.sup..crclbar., S.sup..crclbar.2, CH.sub.3 CO.sub.2.sup..crclbar. ; with reaction times ranging from 0.2 to 8.0 hours at a temperature of 110.degree. C. and molar ratios of Nuc.sup..crclbar. /R-X/Cat. ranging from 1.5/1/.01 to 4/1/.01. However, Chiles and Reeves do not disclose or suggest the use of a triphase catalyst for the production of 2,6-di-tert-alkyl-4-alkenyl phenols. In fact, the procedure disclosed by Chiles and Reeves discloses a reaction wherein the final product is an ether and not para substitution of a dialkylated phenol.